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Extending the gascolator drain thru the lower canopy

Flyer2017

Active Member
I bought a RV-9A built in 2003. (I'd love to build but don't have the time.) It is a great plane but has some squawks I'd like to fix. One squawk is that the gascolator drain is not extended below the cowling. It has been that way since it was built and means the drain only gets used at annuals! The previous owner said it was never a problem as there are drains on both wing roots.

The gascolator is mounted on the lower right firewall and if it was extended straight down it would have to pass thru the hinge material. It seems I need to bring it away from the firewall with a pair of 90 degree fittings and then down to exit forward of the hinge material. I'm concerned that the steel plumbing pipe necessary to do this will be unsupported and will vibrate in flight creating a possible problem. The drop needed is about 4 to 5 inches to exit the lower cowling. The alternative is to just bring it out past the hinge with two 90 degree fittings and reinstall the drain. Then I would make a hole in the cowling large enough to insert a fuel tester and attempt to hit the drain with the tester probe.

Thoughts? Thanks
 
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Or...put a 45* fitting on the gascolator bowl, then reinstall the drain valve. A hole it the cowl would allow you to insert the fuel sampler. That is how the gascolator drain on my RV-6 is mounted.

finish95.jpg
 
I have an fuel screen between my gascolator and fuel selector so I only check my gascolator when I have the top cowl off. I place a cup below the gascolator, turn the pump on the drain into the cup. I've never found anything.
 
Or...put a 45* fitting on the gascolator bowl, then reinstall the drain valve. A hole it the cowl would allow you to insert the fuel sampler. That is how the gascolator drain on my RV-6 is mounted.

finish95.jpg

Similar on my RV-6. Just a HOLE in the lower cowl that the sample cup fits through. I think the hole is about 1" in diameter. Keep in mind that you will get nothing out the gascolator drain if you do not have the boost pump and fuel turned ON.
 
Gascolator

The elegant solution is a Cessna gascolator with a cable attached to drain handle next to oil door. Many of the late Cessna singles have this. The Cessna gascolator is much more robust. Gets rid of the flimsy wire bowl retainer.
The firewall gascolator can also contribute to vapor lock. If your airplane is working ok this should not be an issue.
On any low wing airplane the tank drain is much more important than the gascolator.
Hypothetical: pour a quart of water in the right tank. let it settle and take a sample from the gascolator. You will need to drain a lot of liquid before you start to see water, probably something on the order of 1 to 2 full cups. WAY more than the capacity of any sample cup. Now lets say you took a normal sample from the gascolator but forgot to sample the tanks. All that water is still in there.
A hard gascolator drain protruding below the firewall is a recipe for disaster in an otherwise surviveable crash. The Cessna gascolator has a 1/4" aluminum tube at the bottom, attach a rubber or plastic hose to that and locate the gascolator so the bottom of the tube is slightly above the firewall.
 
I have an fuel screen between my gascolator and fuel selector so I only check my gascolator when I have the top cowl off. I place a cup below the gascolator, turn the pump on the drain into the cup. I've never found anything.

If it's water you are checking for, I think that maybe because the lowest spot in the fuel system is at the tank drains.
 
I installed the extension with brass pipe/fittings from Lowes. Secured with tie wraps. Funny I only check it at annual, but then I take the gascolator bowl off so the drain valve extension is in my opinion unnecessary. Vans apparently didn't think it was necessary. Here are a couple of pictures:

2d021997679aea43bb6747c3c9bf12eb31665_IMG_0978.jpg


40087a1c1fa5c17c1545c95b52d0db2d31665_IMG_0977.jpg
 
My concern with anything that comes down to the level of the cowl is that it is subject to being ripped off, resulting in a spray of pressurized (if the aux pump is on) fuel at an innoppurtune time.

Chris
 
Thanks for the feedback.

Thanks for all the feedback. The previous owners never found any water in checking the gascolator and I haven't either. I agree with the thought that extending it to the lower cowl leaves it liable to being snapped off in an accident and spewing fuel, although the C172 I flew had several fuel drains in the lower cowling. I guess I'll leave it alone for now and check it when I have the upper cowling off for other reasons.
 
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